What is a Wavelength?
The laser wavelength is represented by the symbol λ, with units of nm.
It is determined by the bandgap of the crystal material of the active layer and the resonator length of the chip structure.
Although there are many candidates for the oscillation wavelength within the resonator length, the laser wavelength at which the most gain is obtained around the bandgap will oscillate.
When the junction (active layer) temperature rises, the resonator length increases physically along with the refractive index, so the laser oscillation wavelength will become longer when the case temperature and light output increase.
Heat Affected Zone
The heat affect zone is the region adjacent to the kerf that has been thermally affected by the laser-cutting process. This region is affected by the cutting process in two ways. One is the surface discolouration produced due to the oxidation reaction. This surface oxidation is not permanent and can be removed by as simple a process as sanding the affected region. This region can also be easily measured by optical instruments. The second form of the heat affect zone is the heat-treated zone adjacent to the cut-edge. This region is narrower than the surface oxidation region, and can only be measured through a micro-hardness test. Because of the difficulty associated with making hardness measurements, it is standard practice to report only surface oxidation. The heat-affected zone width increases as the energy input per unit length and the cut thickness increases. Although not normally included in the quality assessment of a laser cut, HAZ width is important when cuts are to be made near heat-sensitive components. It may place a maximum limit on the incident beam power or cut thickness, or a minimum limit on the cutting speed.